The
larvae of many flies (Diptera), moths (Lepidoptera), sawflies (Hymenoptera)
and beetles (Coleoptera) feed within the leaves and stems of plants.
As they feed and grow, the larvae move through their host plant's
tissues, often creating characteristic mines.
A
knowledge of a mining insect's host preferences coupled with the
often diagnostic features of the mine and the lifestyle and form
of the immature stages of the miner enable many species with known
hosts to be identified, frequently more readily than the insect
itself. Such is the state of our present knowledge, however, that
adults should be reared whenever possible to be certain of their
identity and to confirm the miner/host plant association.
A total of 885 insects are recorded as miners in Britain and Ireland. More than 1,100 species are discussed here, although not all are miners as all agromyzids recorded in Britain and Ireland whether miner or not are included. The majority of miners
are moths in the families Acrolepiidae, Alucitidae, Batrachedridae, Bedelliidae,
Bucculatricidae,
Coleophoridae,
Cosmopterigidae,
Crambidae, Depressaridae, Epermenidae,
Eriocraniidae,
Gelechiidae, Gracillariidae, Glyphipterigidae, Heliozelidae,
Incurvariidae,
Lyonetiidae, Momphidae, Nepticulidae,
Pterophoridae,
Roeslerstammiidae, Tineidae, Tischeriidae, Tortricidae, Yponomeutidae,
Ypsolophidae and Zygaenidae. The next
largest group are flies in the families Agromyzidae, Anthomyiidae, Chironomidae,
Dolichopodidae,
Drosophilidae, Ephydridae, Psilidae, Scathophagidae, Sciaridae, Syrphidae, Tephritidae.
The third largest group are beetles in the families Buprestidae, Chrysomelidae and Curculionidae. The smallest group are hymenopterous sawflies (Tenthredinidae).
Scope
This
account of mines is concerned solely
with British insects, although known host associations elsewhere are given.
The majority of Diptera mines
can be readily distinguished from those of moths, sawflies and beetles.
Diptera mining larvae typically cut a semi-circular exit through
the leaf epidermis, whereas moth, sawfly and beetle larvae chew
a hole. The larvae of diptera, often called maggots, also lack a
head capsule and legs, but have a characteristic chitinised cephalo-pharyngeal
skeleton.
The
majority of British leaf- and stem-mining flies belong to the family
Agromyzidae. The only comprehensive account of this family in Britain
is that of Spencer (1972 (out of print)). Although this includes a checklist of
the then known host plants by family and their miners, the diagnostic
features of the mines if mentioned are only described within the
species-oriented keys to adults. Moreover, since this account was
published, further host plants have been confirmed or rejected;
a number of species new to Britain have been recorded; and the systematics
of the family has undergone considerable revision (see Spencer,
1990).
Not
all of the species of Agromyzidae recorded in Britain are leaf-
and/or stem-miners, some such as Agromyza
erythrocephala, Phytomyxa
wahlgreni, Melanagromyza
cunctans and the three species of Hexomyza
are gall-formers and Melanagromyza
fabae is a root-feeder. Others, such as most other species
of Melanagomyza,
species of Phytobia
and many others are stem-borers. In addition Gymnophytomyza
heteroneura, Liriomyza
lutea and eight species of Phytomyza
are seed-feeders; and Phytomyza
nigritula and Phytomya
soenderupi are petiole miners. The lifestyle of 58 species
of Agromyzidae is currently unknown and even when the lifestyle
is known, the host plant may be unknown. For the sake of completeness,
all British species of Agromyzidae are included here, whether or
not they are leaf- or stem-miners and whether or not their host
plant is known.
In
addition to the species of Agromyzidae
discussed here, this account covers the species of British insects
which are or have been recorded as miners.
Scientific
names of miners used here follow Fauna
Europaea. Scientific and common names of host plants used
here follow the Botanical
Society of Britain & Ireland (BSBI) checklist.
Economic
importance
The
damage caused by some mining flies to crops and ornamental plants
can be of economic significance. Several agromyzid pest species
are recorded in Britain. The Cereal leaf miner, Agromyza
nigrella (Rondani), is a serious pest of wheat; Agromyza
nigrociliata Hendel is potentially a serious pest of cereals;
the Tomato leaf miner, Liriomyza
bryoniae (Kaltenbach), is a significant pest of several
genera of cultivated plants; Napomyza
cichorii Spencer was described as a serious pest of cultivated
chicory in Belgium and the Netherlands; and the Cabbage leaf miner,
Phytomyza rufipes
Meigen, is a common pest of Brassica
spp. In addiiton the anthomyiid Pegomyia
betae is a notorious pest of beet.
In
addition to these pests, three other polyphagous non-British species of agromyzid,
Liriomyza huidobrensis
Blanchard (the Vegetable leaf miner), Liriomyza
sativae Blanchard and Liriomyza
trifolii (Burgess) (American serpentine leaf miner), have
been intercepted on ornamental and vegetable crops at their point
of entry into Britain. Although they are not British, they are included
in the lists and notes. All records on particular hosts are noted
and summary lists of the recorded hosts world-wide by host plant
family and genus are given.
The
keys
Keys by host plant genus are provided for all known mines discussed, although some of the records require confirmation
and some of the records are based on non-British associations. In
addition links to keys for related genera are included. More
than 14, 000 host plant or putative host plant associations are
included, although only some 5, 000 of these are based on British records.
Access
to the keys is provided by scientific
and where possible by common name
(only about 52% of the vascular plants recorded in Britain have
common names). Many of the miner/host associations are based on host
genera only.
An additional key is provided to the species of Liriomyza recorded in glasshouses and/or quarantine interceptions.
Reliability
of fly/host associations
Unfortunately
host records in the literature are frequently ambiguous, it is assumed
for the purposes of this account that records in local faunas (e, g,
Stubbs
& Chandler, 1978; Robbins, 1983, 1989 and 1991) refer to British
records, unless stated to the contrary, although this may not necessarily
be the case.
Some
published records are considered here to be erroneous due to either
misidentification of the host or the miner. Such errors are noted
in text. Host insect/host associations cited here from the literature
can be considered most reliable if represented by voucher specimens
of both the mines and reared adults, as is sometimes the case in
The Natural History Museum's collection (which includes the important
collections of leaf- and stem-mines of Emmett, Griffiths, Hering,
Spencer & Parmenter).
Notes
on species
A
single page is devoted to each species of insect. Where known the lifestyle
of all included species is given along with a description of the
mine and diagnostic characters of the larva and puparium; the host
preferences in Britain and elsewhere; the time of year when mines
(or larvae) and adults may be found in Britain; and the known distribution in the British Isles and elsewhere.
Images
More than 2, 800 images of mines, larvae, larval cases, puparia and adults are included.
As far as possible these images are of freshly collected material.
Images
of 326 host plants have also been included. Links to images of host plant species in British Wild Flowers by John Somerville et al. are also provided.
All
images are the copyright of the relevant photographer.
Parasitoids
By far the most important mortality factor are parasitoides. Very commonly, when opening a mine, one can encounter a parastoid larva that is sucking the liquified body contents of its host. It is impressive to see how an, often quite small, parasitoid, has overpowered its victim that is almost motionless and has its body colour and transparancy totally altered.
Several hundred species of British and Irish Hymenoptera parasitoids
have been recorded on British and Irish miners and these are included in lists by superfamily and family and on relevant species pages. |